Hille, R. ; Pomplun, E.FZJ* ; Brunen, E.FZJ* ; Möllmann-Coers, M.FZJ*

2003
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich

Report No.: Juel-4057

Abstract: Within the framework of aprobabilistic investigation, emission reference values have been calculated for the nuclide groups iodine, caesium, noble gases,and `other nuclides' taking real weather sequences into account$^{2}$. With these values, the guideline dose value for the initiation of protective measures are not exceededin 95% of all cases. The calculation is performed not only for the initial value for taking protection measures (0.01 Sv effective dose, 0.05 Sv thyroid dose for children) according the guidelines for the civil protection in the surrounding of a nuclear facility [GMBI,1999], but also for the upper guideline values (0.05 Sv effective dose, 0.25 Sv thyroid dose) according to SSK [1995]. The latter allow comparison with the current values [GMBI,1988]. The investigations have been performed for infants (>=1y) andadults (> 17y), and are based on the year 2000. The composition of the different nuclide groups is based on the inventory data of a power reactor after 100 doperation time and a decay time of 0 h and 240h, respectively. There lease factors were taken from the `Deutsche Risikostudie Kernkraftwerke 1979 '[SSK,1989]. The reference values were calculated for the release heights 20, 50, 100, and 150m, at each case for 0.5,1, 3, and 5 km distance from the damaged reactor. The dose calculation was performed according to the `Störfallberechnungsgrundlage' [SBG,1994]. The reference values vary depending on the source distance and the decay time. With increasing distance and corresponding atmospheric dilution the values increase by a factor of 3 to 10 between 0.5 km and 5km, depending on the nuclide group and the emission height. Between 0 h and 240 h decay time the emission reference values increase for noble gases, and decrease for iodine and other nuclides. They remain constant for cesium. This behaviour depends on the half life of the dose determining nuclide relative to the others in the respective group (long living I-131, short living Kr-88). For the upper dose reference values at 0.5 km source distance and 0 h decay time a rather good agreement was found for infants with those values which are given in SSK [1995] for the declaration of a disaster alarm. In this case, the given factor of 10, by which the iodine reference values obtained only with I-131 measurements are reduced, is very conservative.

Keyword(s): reactor accident ; radioactive emission ; alarm system ; reactor safety

1. Abteilung Sicherheit und Strahlenschutz (S)